This invention relates to silicon web growth technology. Dendritic web silicon substrates are produced for solar cell manufacturing, by growing thin ribbons of single crystal material from the surface of a molten pool of silicon. The silicon melt at a temperature of 1412.degree. C. is located beneath a temperature regulating lid and heat shield stack. This process is described in more detail in Seidensticker, Journal of Crystal Growth, 39, 1977, the disclosure of which is hereby incorporated by reference. In this radiatively controlled system, view factors from the melt through the lid/shield structure play a very important role in defining the critical temperature distributions within the hot zone. A primary determinant of this view factor is the location of the melt surface relative to the lid. These temperature distributions affect the inherent ability to grow single, crystal material, the stability of growth, and crystal stress. Maintenance of a constant melt level over long periods of growth is necessary to achieve constant temperature distributions for steady state growth. In addition, growth of long crystals requires continuous melt replenishment to maintain a continuous source of liquid silicon.
Replenishment of the melt requires a high resolution, slowly responding control system which adds replenishment material at a steady, slowly varying rate (on the order of 0.2 g/min.) Discrete batch feeding introduces significant thermal perturbations to the melt and is therefore an unacceptable method. Silicon replenishment systems have been developed which enable this continuous replenishment, but a method of providing